They don't do it know, because of all the antitrust shit that will rain over them.
The only way would be if Microsoft suddenly wouldn't be a monopoly anymore. But If Microsoft will not rule the market anymore, why should the manufacturers close their products to the other players on the market.
Microsoft won the browser wars in the beginning, but look at the browsers now, in the long run there was competition. I think that the same will be with the OSes, they won the OS wars in the beginning, but we will see diversion again.